Draining paving tiles made of dredged sludge

Dutch start-up Waterweg developed a way to reuse dredge by turning it into water-permeable street tiles, offering a sustainable way to counter flooding in cities.

To prevent canals and rivers from becoming silted over time due to sedimented sand and mud and thus becoming too shallow to navigate in urbanised areas, the waterways need to be dredged every once in a while. This dredged sludge is now often seen as waste and disposed off, which costs a lot of time and money.

The founders of Waterweg (which in Dutch means both ‘waterway’ and ‘water away’) met each other during the BlueCity Circular Challenge in 2018, where they were asked to find a way to reuse dredging sludge in a local application. Because urbanised areas often have to deal with flooding, the team decided to create draining paving tiles.

To make the tiles, the sludge is mixed with lime and a little cement, in a ratio of 90 per cent sludge and 10 per cent additives, before the material is compressed into the tiles using the Compressed Earth Block method. The mixture is then left to dry. The tiles are designed in such a way that water can easily pass and infiltrate into the ground.

Because cement generates a lot of CO2, the team is currently experimenting to see if they can replace the additive with more sustainable geopolymer concrete.

Two weeks ago, a trial street of 2 square metres was laid in the city of Delft in the Netherlands, to see how the tiles will behave. Waterweg’s aim is to pave a whole neighbourhood in Rotterdam within 3 years.

Aside from paving tiles, the start-up plans to create all kinds of construction materials using dredge.

Currently, Waterweg is working on upscaling the production process to be able to pave bigger areas.

Photos: Waterweg / Jasmijn van der Linden